Several systems for detecting rough road surfaces are known in the automotive technology.
According to the German Patent Application No. 38 27 737, entitled a Device for Generating an Indicating and/or a Control Signal, the use of the device disclosed therein makes it possible "to recognize and signal critical changes in the road-surface covering with relatively little time delay" (col. 3, lines 57-60). To this end, signals which are primarily used to regulate the automobile chassis are processed accordingly.
The German Patent Application No. 36 10 186 concerns an anti-lock braking (ABS) control system. Since known ABS control systems monitor wheel-speed signals to regulate braking pressure, it is important that wheel speed patterns caused by a rough road surface are not mistaken for lock-up tendencies of the individual wheels caused by braking.
In known applications involving the monitoring of exhaust gas from internal-combustion engines, detection of misfirings is critical. A misfiring occurs when the air-fuel mixture in a combustion chamber of an internal-combustion engine is either partially burned or not burned at all. As a result, pollutant-containing exhaust gases are produced.
Since misfirings in an internal-combustion engine cause short-term drops in the engine's rotational speed, such misfirings can be detected by monitoring the speed of the engine for fluctuations characteristic of misfirings. Once a misfiring has been detected, measures can be taken to limit the exhaust pollutant emissions. German Patent No. 41 00 527 (R. 24099) entitled A Method and Device for Determining Misfirings in an Internal-Combustion Engine discloses and clarifies the difficulties that such misfirings entail. If engine speed is used to detect misfirings, measures need to be taken to avoid misinterpreting a rough road condition as a misfiring since both will effect engine speed in a similar manner. The present invention provides a system that solves the problem of detecting rough road conditions without the problems identified in the prior art.